This invention relates to a buried type semiconductor light emitting device which can be applied to an OEIC (opto-electronic integrated circuit).
The semiconductor laser is presently used as the light source of optical communications or optical disks, and it is expected to be further applied to OEIC and others. However, since the usual semiconductor employs the cleavage surface as resonator, the length of one side of a chip is limited by the resonator length, and it is difficult to integrate other elements. For example, if the laser's resonator length is 200 .mu.m, the length of one side of an OEIC is 200 .mu.um, and when it is attempted to integrate four electric elements, the length of other side must be 1 mm. When integrated further, the slender ratio of the chip becomes greater, which makes it difficult to divide or assemble chips. While the laser to form the resonator by etching is also being developed satisfactory resonators are not available at the present time.
As an example of a conventional semiconductor laser, a buried type semiconductor laser is known (see the Journal of Applied Physics, Vol. 53, pages 1364-1372, 1982), and it has the following advantages.
(a) Since the InGaAsP active layer is surrounded by InP which has a low refractive index, the light is enclosed, and the laser is oscillated at a low threshold current.
(b) Since the p-type InGaAsP contact layer is wider than the InGaAsP active layer, the contact resistance with the Au/Zn electrode may be lowered.
In spite of these advantages, the conventional buried type semiconductor laser involves the following points to be considered.
(a) In the reverse means shape forming, there is no reproducibility of the shape. That is, the width of InGaAsP active layer is determined by the width of p-type InGaAsP contact layer and thickness of p-type InP clad layer, and if the thickness of the p-type InP clad layer fluctuates, the width of the InGaAsP active layer also varies, which results in a defective characteristic.
(b) In the crystal growth of burying the reverse mesa shape in the p-type InP block layer and n-type InP buried layer, the side of the InGaAsP active layer is damaged by heat, which may cause a reduction in the quantum efficiency or an increase in the leakage current.
(c) Since the stripe direction is &lt;011&gt; directions, that is, the resonator surface is (011) surface, the etched mirror cannot be formed by chemical etching.